# Cirrus sr 20 fuel consumption and other details

Hi everyone,

I am currently doing a design project on Cirrus SR 20, mainly performing analysis for this aircraft and then comparing the results what I have calculated with the real values. I initially started with takeoff weight estimations and selected the mission profile. I had doubts in the fuel consumption:

The estimated fuel for engine start, taxi and takeoff is 1.0 gallons (6 lbs). Therefore, after fuel consumption during warm up and takeoff the weight reduces to 6 lbs less that is 2994 lbs. The weight fraction for takeoff and warm up is 0.998

For climb (1-2) the amount of fuel consumed is 2.4 gallons (14.4 lbs). Therefore, after the fuel consumption during climb segment the weight reduces to 14.4 lbs less that is 2979.6 lbs. The weight fraction for climb is 0.995

For cruise (2-3) the amount of fuel consumed is 41.4 gallons (248.4 lbs). Therefore, after fuel consumption during the cruise segment the weight reduces to 248.4 lbs less that is 2731.2 lbs. The weight fraction for cruise is 0.916

For Loiter (3-4) the amount of reserve fuel for 45 minutes is 8.3 gallons (49.8 lbs). Therefore, after fuel consumption during loiter the weight reduces to 49.8 lbs less that is 2681.4 lbs. The weight fraction for loiter is 0.918

For landing (4-5) the amount fuel required is unknown to me. Since in the manual the usable fuel is 56 gallons. Till now what I have calculated above shown is 53.1 gallons, therefore remaining fuel is 2.9 gallons which is not possible for landing.

Can someone guide me please. It would be great help.

Regards,

Varun

The reserve fuel is not meant to be used.

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Asus Nexus 7

In manual its reserve fuel for 45 minutes , so what fuel will they use for loiter ?

if total usable fuel is 56 gallons for Cirrus SR 20. The below information is given in the manual on page 129.

The total estimated fuel required is as follows:

• (0-1) Engine start, taxi, and takeoff … 1.0 gallons
• (1-2) Climb … 2.4 gallons
• (2-3) Cruise … 41.4 gallons

Now for (3-4) loiter and (4-5) Landing is not mention instead,
• Reserve … 8.3 gallons
• Total fuel required… 53.1 gallons

So should I take reserve fuel for loiter as I took or it not suppose to be?

Thanks for your information.

Regards.

We don’t usually loiter. If you plan to do so you need to allow fuel for it, in addition to the reserve fuel.

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Asus Nexus 7

Thanks

May be. I think for general aviation aircraft they don’t loiter, just checked a book.

Is there any way to find the fuel consumption for landing and descent what should I assume ?

Regards,

Varun

In my SR20, I count on fuel for a 10 -15 minutes IFR approach. However, my personal safety margin is destination +15 gal usable left over, IFR/VFR doesn’t matter. Also you showed 41 gal in cruise. That puts someone in the plane for over 4 and a half hrs … a long time. A 20 can also be leaned, in cruise, back to 9.4 to gal hr, depending on Alt, and still be moving along pretty good and keep the CHT’s in a comfortable range.

Hi

Is the fuel consumption same for landing and takeoff. Since for my weight estimation its important to know the weight at each point. I know for taxiing, takeoff its 1 gallon.But not sure of descent and landing. Once I know the fuel consumption in these two profiles I can easily calculate the design gross weight for my analysis.

Is there any possibility to get information for how much payload and crew members they assumed when entered the total weight in the manual?

Regards,

Varun

Varun,

Perhaps if you could break down for us exactly what information you need and why we could give you a better answer. The book may say 1.6 gallons for taxi and take off but what if you’re in a conga line and have to wait 45 minutes for departure? I plan based on my location and mission. Please be more transparent with your question. [Y]

Varun,

Let me echo Tony and the others in saying that it really isn’t clear to us exactly what you are trying to figure out.

Fuel consumption has many variables. Prior to takeoff for example it will vary depending on which runway you have to get to (at my airport the nearest runway to my hangar is about 0.1 miles while the farthest is 1.25 miles. Clearly the fuel used will vary with the runway in use. Temperature matters as well. In winter I may have to run the engine 10+ minutes just to get the temps up to takeoff levels while in the summer I might be ready to depart just a few minutes after startup. The fuel used will clearly be different. Climb rates also vary with temperature. You will use different amounts of fuel to get to different altitudes under different conditions.

When we descend there are different techniques used by different pilots. Some pilots maintain an airspeed and reduce power while others increase their speed (point the nose down) and leave the fuel flow the same. The fuel used therefore may differ slightly depending on the pilot’s technique.

Approach and landing also is variable. If you’re heading east and the airport you’re going to is landing east, you will use less fuel on your approach than if the airport is landing to the west. An approach with a procedure turn will consume more fuel than a vectored straight in. The list goes on.

The manual simply lists a maximum takeoff weight. It assumes no specific weights for passengers although that is importand to calculate the center of gravity. Incidentally, if you know you are going to burn x gallons from start up to takeoff it is perfectly legal to start your engine at a weight of Maximum Takeoff + x. You just are not allowed to takeoff above the maximum weight. (Some airplanes have a maximum ramp weight as well and that limits the weight at engine start).

I presume you want this information for some theoretical exercise. If so, it would be best to let us know exactly what you are trying to do and I’m sure we’ll help as best we can, but from a pilot’s practical perspective all that matters is that you plan your flight so that 1) you obey aircraft W&B limitations and 2) you carry enough fuel to get to your destination, any required alternate and have a reserve that meets the legal requirements, or, better, at least one hour in the tanks when you land based on a typical cruise setting.

Hi

Thankyou for your comment. I really appreciate your help. Actually I am doing a aerospace design project for my college to develop a pilot trainer aircraft by making a concept design. So I need to analyse any one airplane and then create the concept design from the selected plane. So I selected Cirrus SR 20 airplane, when I perform calculations for my concept design it should be close to Cirrus SR 20. Its basically like case study and then designing it.

1. Can I know what is maximum limit for each passenger in Cirrus SR-20 . How many pounds ? Total there are four passengers on this plane including pilot.

2. Is there any way to get details of what aerofoil they used for this plane ? Any aerodynamic data related to this I can get like graphs etc. for doing my case study?

Hope you reply in your busy schedule.

Best Regards,

Varun Kumar

Varun,
You can download the POH at no charge from the cirrus website

Sir

I have downloaded the POH but the max. weight for each person is not mentioned, just the max. baggage allowance is mentioned which is 130 lbs. Even the airfoil data wasn’t present but I found out on one website which says **Roncz Airfoil. **

Can always call up their service hotline

Varun,

Total weight and “weight and balance” is more important than the max weight of each person. In other words the maximum weight of each person is dictated by the weight of the other occupants and baggage. Just because there are 4 seats does not mean that you will be able fill them.

You mention that this is for a project. I highly recommend that you read the POH from cover to cover. Enlist the help of an instructor to decipher the things that you do not understand.

There is no maximum weight per passenger. As long as the total weight and balance of the occupied seats and baggage compartment is not exceeded, the total weight per seat is not a limitation.

The baggage compartment has a weight limitation because of its location longitudinally in the plane… If you put more than the 130 pound limitation back there, your center of gravity, particularly as you burn fuel and give up weight further forward, will be exceeded at the aft limits.

But the 4 passenger/ pilot seats are clustered close enough to the CG that each seat does not have a weight limit other than the total weight allowed.

Hope that helps.

I have never heard a reference to the maximum weight of any one occupant. My SR20 does seem to fly a little differently when it is loaded more on one side or the other but it is not really a big deal. The weight and balance calculations are all based on the front seats as a pair and the back seats as a pair.

“Cirrus Proflite” is a good Iphone/Ipad app for w&B . I think it is free but I might be wrong. You might find it to be useful. There are other apps available. You can get “SR20 POH” for 10 dollars as well, but download of the POH is free from Cirrus if you just want it for your laptop.

The cirrus is in fact a really good trainer, but it is more expensive than most. A slightly older Diamond DA20 might be a better plane to emulate, since cost is always the major factor in trainer plane selection and most flight instructors go with used aircraft.

Most (90 plus %) training flights are not at all like straight and level long distance flights, so if you are really designing an ideal trainer you should be looking at the kind of flights that students actually make. Talk to a real world flight instructor or two to get an idea of the wide range of mission profiles that exist. Take that argument to your professor, use a composite mission profile and you will get a better grade. Engineering is supposed to fit design to the real world.

thanks a lot .[Y]